Radio system and apparatus



Aug. 21, 1934. w 1,970,640

RADIO SYSTEM AND APPARATUS Filed May 19, 935 2 Sheets-Sheet 1 Aug. 21, 1934. R, WISE 1,970,640

RADIO SYSTEM AND APPARATUS Filed May 19, 925 2 Sheets-Sheet 2 7/ En /727' -55 Amp/W227; J4

Ill VENTOI? #14; ,4 rronus s Patented Aug. 21, 1934 RADIO SYSTEM meme Roger M. Wise, lOakIand, laliirl, assignor to E..T.

Cunningham, San Francisco, Calif.

Application May 19, 1925, "seria No. 31,288

2 Claims. (01; 179-171) This invention relates to a systemoperating by radio, and to apparatus especially adapted for use in such systems. More particularly, my invention relates to radio receiving. systems. in

p 5 which audions are used for amplification or de tection.

It is now quite common to utilize one ormore tuned circuits in radio receiving systems, where by selectivity is secured, with respect to the fre quency of the carrier wave. Especially are such circuits of benefit in connection with radio frequency amplifier stages, whereby a succession'of tuned. circuits can be usedfwith the succeeding stages, so that the selectivity is gradual1yfincreased. Tuned circuits are also used iniconnection with regenerative detectorsystems, having a feed-back arrangement for coupling the input and output circuits of the detector. Y f

When radio frequency amplification with vacuum tubes is used, it has been'founddifiicult to keep the vacuum tube circuits stable. Such. vac uum tubes usually have an electron emitting electrode, such as a heated filament, apositive plate electrode to which the electrons are attracted, anda control electrode that afiects the -fiow of electrons in response to Variations in'its potential with respect to those of the other ltwo electrodes. The control electrode is usually in terposed between the plate and thefilamen't, -and is inthe form of a grid onscreen, that permits electrons to pass without material hindrance. The instability of radio frequency'circuits 'asso-'- ciated with such a vacuum tube is manifested as a'tendency to sustain undesired'oscillations, and is due in great measure to the capacity existing between the electrodes; especially between the grid and the plate. j I It has been common to. overcome some of the badefiects of this parasitic capacity 'by' the aid of a neutralizing circuit, which sets up electrical conditions opposing those produced by or due to the parasitic capacity coupling. "Such schemes have been found very eflicient; but theneutralizing circuit it has been fourid will serve most efiic iently onlyfor a restricted band of radid ire quency operation, the band being dependent upon the electrical characteristics of the neutralizing circuit. In order to secure the beneficial effects for a wide range, it is necessary to adjust the neutralizing circuit as the frequency of operation varies. .J F

It is one of the objects of my invention to make it possible to adjust such a neutralizing circuit automatically when the tuning of the main circuits is being performed. This-can be accomplished for e z ampleby mechanically interconnecting the tuning devices associated with the neutralizing circuit and ,with the tuned radio frequency circuits. Nevertheless I prefer to accomplish this result by the aid of a novel condenser structure, used fortuning the input circuit 'or circuits, of the radio frequency amplifier. Itis therefore another obj ect'of my invention to' provide acondenser structure whereby these beneficial results can be obtained.

condenser structure that I utilize for th purpose hereinbefore stated can as well be used in c'onn'ection with regenerative feed-back circuits. I In such circuits, there is a so-called tickler circuit? which serves to transfer energy between the input and output circuits of the dctectortube. I It is found that for most efficient results, tlfistickler circuit should also be adjusted in ac'cor'dance with the frequency of operation. With the. used my novel condenser, the tickler circuit cause so arranged that it, is automatically adjusted when tuning'thejmain circuit, and it therefore still: another object of my invention to render this beneficial result possible. i I ,My inventionpos'sesses other advantageous features, some of which, with the foregoing, will be set forth at lengthin the following description; where I shalloutline in full those forms of my invention which I have selected for illustration in the drawings accompanying, and forming part of the present specification. Although I have shown in the drawings but a few embodiments of my invention, I donot desire to be limited thereto, since the invention as defined in the claims may be embodied in other forms also.

Referring to the drawings: Figure 1 is a rear view of one form of condenser which is'constructed in accordance with my inv iq t Fig. 2 is" a in-Fig. l; h 3 Fig. 3 is a wiring diagram of a radio receiving system using a neutralizing circuit, in which system my invention is embodied; and i .Fig'. 4 is awiring diagram of a regenerative receiving system embodying my invention. V

In the present instance I illustrate my invention in conjunction with a condenser structure that is described and claimed in a prior application filed on Julyv 26, 1924, in my name, entitled Variable lcondenser andhaving Serial Number 728,480, patented Feb. 221927, #1518399. It is however, possibletouse other forms of variable tuning devices, such as other forms of variable condensers or inductan'ces. In all such devices there is at least one top plan view of the condenser shown movable part; in the case of condensers such as illustrated, there are usually relatively movable condenser plates. In the present instance, both sets of plates 11 and 12 are movable to interleave to any desired extent. Each set includes a plurality of spaced fiat plates having apertured cars such as 13, between which tubular spacers 14 are located. These tubular spacers. are preferably soldered to the cars 13, whereby good electrical contact is secured between all of the plates of a set, and the complete assembled ears and spacers are rotatably mounted on stationary rods 15 and 16. The spacers 14 are so designed that the plates 11 and 12 interleave as movement is'imparted to one or both of the sets of plates.. p

In order further to increase the rigidity of the plate structure, each plate is provided with a pair of tabs such as 17 and 18, chest the top and the other at the bottom of the plate. These arebent so as to form an overlapping structure of all of the top tabs and of all of the bottom tabs for each set of plates. These overlapping portions can be soldered or otherwise joined to form substantially a rigid bar connecting all of the plates of a set together. r

In order to rotate the sets of plates inopposite directions, so as to bring them as desired to any relative position between the fully overlapped one shown in full in Figs. 1 and '2, and the entirely free positions shown in dotted lines in' Fig. 1, I provide a pair of intermeshing gears '19 and 20, which are attached respectively to the plate-ass semblies 11 and i2, and have axes of rotationrespectively coinciding with the axes of rods 16 and 15. These rods are held fixed in'a'supporting disc 21 of insulation material", as by passing through bossesj 22 provided on said disc; -The gears 19 and 20 are of coursealso' madefrom' insulation material, and are rotatable on the stationary-rods 15 and 16. Where these rodspas's through the disc '21, washers'23 maybe provided.

The plate assemblies-11 and 12 areheld-lniplace againstaccidental axial movement along the rods 15 and 16, by the aid of a strip 24 'ofinsulation. This strip serves also vto stiife'n the condenser structure, and is tightened in place by the binding post structures 25 and 26. "I'l' e partsare tightenedonly sufiiciently to. createsuflficient friction between the. moving elements jwhereby they may be left in an adjustedpositionwithout danger of accidental disturbance. r

Each of the binding posts 25 and 26 serves as one terminal of the condenser. They are connected respectively to theisets of plates 12 and 11 by the aid of pigtails 2'7 and 2.8.

Rotation is imparted to'the intermeshing' gears wand 20 by the'aid of a pinion 1 that .meshes with one of the gears, for example 20. This pinion is arranged to be manually rotatedbythe aid of a shaft 32 connected thereto and extending through a main supporting panel 33. The shaft 32 is held against axial movement bythe aid of a forked strip 34 straddling the shaft and held in.

place by a screw 35. At the upper 'porti cn,,this

strip has a bent over part 36 projecting into an apertures"! in the disc 21, andserves'to hold the forked strip 34 more rigidly in place.-

As thus far described, the condenser structure does not differ substantially from that disclosed in my prior application hereinbefore identified. I provide howeverfadditional elements whereby adjustment of the condenser causes a simultane ous variation in the electrical properties of another circuit associated with the condenser. For example, I may provide'a stationary plate structure with which one of the relatively movable structures 11 or 12 cooperates to vary the capacity between it and the stationary structure as the condenser is adjusted. In the embodiment of Figs. 1 and 2, I show a fiat plate 38 which is supported close to the end plate of the structure 12, on the insulation strip 24. This plate may be fastened to the strip by the aidof a binding post structure 39 serving as a terminal for the plate 38. The plate 38 in this instance has such configuration that the capacity between it and the plates 12 increases as these plates 12 are moved outwardly from the other set 11; or in other words, when the capacity between sets 11 and 12 de- '.creases, that between set 12 and plate 38 increases, and vice versa. Nevertheless, it is evident that the plate 38 could be so formed that these capacities increase at the same time, and decrease atcthe same time. The type of circuit in which the condenser is used, determines this factor. The absolute amount of capacity'between the supplementary plate 38 and the condenser can be nicely adjusted by bending this supplementary plate inward or outward, as indicated in Fig. 2 by the dotted line position 40.

In Fig. 3 I illustrate a radio frequency amplifier system in which my invention is embodied. Only one radio frequency stage is shown, the further stages of amplifiers and detector being indicated merely by a rectangle 41, and it is to be understood that the succeeding radio frequency stages may be entirely similar to that actually shown.

In this case, I have illustrated an antenna absorbing circuit, consisting of the elevated conductors 42, loading coil 43, and a ground 44. The usual tuned circuit, consisting of a coil and a variable condenser 46, is coupled to the loading coil'43,, as by the'aid of' coil 45. The variable condenser 46 is constructed in the manner taught by this application in connection with Figs. 1 and 2.

' The first stage of electronic emission amplifier 47 has its "input circuit connected across this condenser 46. The tube 47 has an electron emitting electrode, such as a heated filament 48, and .a cold electrode or plate 49. It is now well understood that if plate 49 is maintained at a potential positive with respect to the filament 48, the electrons will be attracted from the filament and will thus'form a space current. However, the quantity of flow can be controlled by controlling the potential of a point in the space, as by the aid of the control electrode or grid 50 interposed between the filament 48 and plate 49. The radio frequency energy received in circuit 45-46 is caused "to affect the relative potentials of this electrode 50 and filament 48, whereby the space current is varied in accordance with the relative potentials of the grid and filament.v This variation is of course of a much higher order than the potential variations of grid 50, and it is due to this that an amplifying effect is secured. A battery 51 or other source of electrical energy serves to supply the positive potential to theplate 49.

The variations in the space current cause corresponding variations in the current flowing in the coil 52 connected in the plate circuit. These current variations in turn are translated into potential variations between the terminals of coil and further audio frequency amplifiers and finally to a translating device, such as aloud speaker or phone 54. 3 r a 1 It is-now well-known how-"to prevent unstable conditions of operation due to the interelectrode capacity effects between grid and plate 49. Usually this is accomplished by the aid ofa neutralizing circuit which includes a fixed condenser'of small capacity, and extends between the grid 50 and an intermediate point of coil 53. When such a circuit, properly connected, is used, it is possible by proper choice of constants of the small condenser and of the coil 53, to produce a neutralizing effect between the electrodes 49 and 50. But such a circuit, no matter how carefully adjusted, is theoretically accurately adjusted for but one frequency of operation. When the frequency is varied materially, the neutralization becomes less and less effective. This is due to the fact that the reactance of coil 53, a part of which is in the neutralizing circuit, varies directly as the frequency; and to compensate for this, it is necessary to vary the capacity of the small condenser so that the capacity increases as the reactance of coil 53 increases. 25-

This effect can very readily be accomplished by the use of a condenser such as illustrated in Figs. 1 and 2, for the input circuit of tube 47. Thus in Fig. 3 I show the supplementary plate 38 as cooperating with one of the sets of plates of the condenser 46. This plate, in conjunction with one set of plates of condenser 46, forms a small variable condenser which is included in the neutralizing circuit extending from the grid 50 to an intermediate point of coil 53. When the frequency of operation varies, the condenser 46 is varied to bring circuit 45-46 in tune, and this variation also causes the capacity to vary between plate 38 and the condenser 46. Thus when the frequency is high, the plates 11 and 12 of condenser 46 are interleaved to a less degree than when the frequency is low; however, the reactance of coil 53 is high, and therefore the neutralizing capacity should also be high. This effect is produced by the aid of the structure shown in Figs. 1 and 2, for it is seen that in that case, as plates 11 and 12 move apart, more and more of plate 38 is adjacent the plates 12, which correspond to the upper plate of the condenser 46 in Fig. 3. Therefore it is possible in this way to neutralize the parasitic capacity substantially entirely for a very wide variation in the frequency of operation; and this is accomplished automatically and without the necessity of supplementary adjustments. The compensation produced by the small variable capacity can be made substantially accurate by properly forming the plate 38 so that the variable capacity is always substantially correct for the wave length to which circuit 45-46 is tuned.

In some instances, the supplementary capacity must increase with an increase in the main capacity. One such instance is illustrated in the system of Fig. 4. This system is merely diagrammatic of a tickler coil regenerative receiver using a single detector tube 55. The absorbing circuit 42-43-44 is shown the same as before; and coupled to the circuit is a tuned radio frequency circuit 56, including a variable condenser 57. The tube 55 has a filamentary electron emitting electrode 58, a control electrode 59, and a plate electrode 60. The input circuit includes a small capacity 61 bridged by a grid leak 62 of high resistance. It is now well understood that the grid leak 62 and condenser 61 serve to change the character of the radio frequency pulseswpas'sing to tube 55, in such manner that the audio frequency signal ,superimposedon. the radio frequency carrier wave is predominant in the output=circuit of the tube'55'. Thistype of detection is now sowell understood: that it is unnecessary'to detail it further herein.

.In ordertoincrease-the amplification due to the use of the tube, a feed-back or tickler circuit is included in the output side of the tube, which is coupled to the input side. The output circuit thus includes not only the translating device 63, such as a loud speaker or car phones, but also a coil 64 coupled to the circuit 56. The coupling of the input and output circuits in this manner sets up regeneration, for it permits transferring of energy between the two circuits. The interelectrode capacity, especially between the grid 59 and the plate 60, is an important element in the feed-back circuit, for as the frequency of operation varies, it is found that the amount of feedback also varies. Thus when the frequencies are high, the capacity between the electrodes is productive of a more intimate coupling between the two circuits; and when the frequencies are low, the increase in capacity reactance between the electrodes has the effect of reducing the extent of the coupling.

In the past, these variations in the coupling could be compensated for only by varying the coupling between the coil 64 and the input cirquit. This required an additional adjustment, which is manifestly objectionable. By the aid of my invention, the necessity for such an adjustment is obviated. The supplementary plate 65 of condenser 57 in this instance is so arranged as to have its capacity increased with respect to the upper plate of condenser 57, as the capacity of this condenser is increased. The plate 65 is electrically connected, as by the aid of connection 66, to the feed-back circuit. There is thus an additional capacity coupling between the input and output circuits, and this coupling is variable in such manner by proper design of plate 65 that the total feed-back effect stays substantially constant irrespective of the variations in the frequency of operation. This is accomplished automatically; no supplementary adjustment is needed as the wave length of the received signal varies.

The two embodiments shown in Figs. 3 and 4 are merely illustrative of the types of systems in which my invention can be utilized. The main feature in each is the fact that a supplementary variable capacity effect is obtained with a vari- 130 able condenser, by providing a plate or condenser electrode that cooperates with at least some of the other electrodes as they move to vary the main capacity.

I claim: 135

1. In a radio frequency receiving system, an electron emission device having an input circuit and an output circuit adapted to feed high frequency energy back into the input circuit, means including a variable condenser for securing reverse feed back of energy between said circuits, means including a second variable condenser for selectively tuning said input circuit thru a wide range of radio frequencies, said first named condenser having substantially no effect upon the tuning of said input circuit, and a common control for simultaneously varying the capacitance values of both said condensers whereby the sys tem is maintained in stable neutralized condition for a substantial range of radio frequencies. ea

through a wide range of radiofrequencies, said first-named reactance having substantially no effect upon the tuning ,of said input circuit, and a common control for simultaneously varyingthe values .of both said reactances whereby the system is maintained in stable neutralized condition for a substantial range of radio frequencies.

. ROGER M. WISE.. 

